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Adrenal insufficiency — USMLE Step 3 MCQ

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ModerateInternal Medicine (chronic management)Adrenal insufficiencyUSMLE Step 3

A 41-year-old woman has fatigue, weight loss, hyperpigmentation, and orthostatic dizziness. Sodium is 129 mEq/L and potassium is 5.6 mEq/L. Morning cortisol is low and ACTH is high. Which of the following is the most likely diagnosis?

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Reveal the answer and explanation

Correct answer: D — Primary adrenal insufficiency

High ACTH with low cortisol plus hyperkalemia and hyperpigmentation is consistent with primary adrenal insufficiency.

Reference: Endocrine Society adrenal insufficiency guideline